This invention relates to a document handling apparatus and specifically concerns a means for automatically moving sheets of material sequentially into a predetermined position on a work surface and then moving that sheet of material out of that position to make room for the next sheet.
As will be understood by referring to the commonly assigned U.S. patent application Ser. No. 687,062, now U.S. Pat. No. 4,076,233, filed on even date herewith and which is incorporated herein by reference, quick and accurate movement of documents to a registered predetermined location and removal of these documents is important in the processing of sheet material in environments such as copying machines. In a copying machine, an automatic document handler must not only rapidly move the document onto a platen, but must accurately register that document in a specific predetermined copying position or area to assure the production of a complete and visually acceptable copy. If the document is situated on the platen in a skewed or misaligned position, the copy will reflect this same skew or misalignment and may be incomplete and/or unacceptable to the user. If the original is wrinkled, torn or creased it may not produce good copies and will not be acceptable to the user for a great number of reasons, not the least of which may be unsuitability for subsequent use in a machine or automated processor. Moreover, the automated handler must be able to perform these functions efficiently with maximum range of paper or material weights, as documents copied may vary from light weight paper such as what is known as "onion skin" in the order of 50 grams per square meter to much heavier weights in the order of 120 grams per square meter.
While the prior art has concerned itself with document handling apparatus which moves a document onto a work surface, registers it and then moves it on, it has failed to recognize, so far as we are aware, the invention herein according to which there is provided a document handling apparatus comprising document transport means having a first surface alternately movable in opposite first and second directions and of a material adapted to frictionally engage a document, the apparatus comprising variable friction producing means for providing a high frictional engagement between the transport means and the document when said transport means is moving in said first direction and relatively low frictional engagement between the transport means and the document when said transport means is moving in said second direction.
According to one aspect of the invention the variable friction means comprises a pressure applying means that is positioned in engagement with a second surface of the transport means opposite from the first document engaging surface. The pressure applying means may be pinch roll having an axle, the ends of which project from opposite sides thereof, said axle ends each being engaged in parallel elongated slots inclined at an acute angle to the portion of the first surface of the transport means therebelow, whereby when said transport means moves in a first direction said roller axle is urged down said inclined slot toward said transport means to increase the pressure on said second surface and when said transport means moves in said second direction said roller is urged up said slot to reduce the pressure on said surface.
According to another aspect of the invention the variable friction means comprises a means for pushing or pulling said first surface of said transport means whereby when said first surface is pushed it exerts a lower coefficient of friction with the surface over which it is pushed than it would exert against same surface when it is pulled.